1. Field of the Invention
The present invention relates to a method for manufacturing a laminated ceramic electronic component, and more particularly, the present invention relates to a method for manufacturing a laminated ceramic electronic component such as a laminated ceramic capacitor, laminated inductor, and laminated LC filter.
2. Description of the Related Art
FIG. 1 is a schematic diagram showing the manufacturing process of laminated ceramic electronic components such as laminated ceramic capacitors, for example, as described in Japanese Patent Application Kokai No. H5-92406. In a manufacturing apparatus 10 described therein, a carrier film roll 12 around which a carrier film formed from a synthetic resin or the like is rolled up is first prepared. The carrier film 14 is pulled out from this carrier film roll 12, and the surface of the carrier film 14 is coated with a ceramic slurry 18 by a coating apparatus 16.
The carrier film 14 that is coated with the ceramic slurry 18 is sent to a drying apparatus 20 so that the ceramic slurry 18 is dried, after which the carrier film 14 is temporarily rolled up by a take-up apparatus 26. Thus, a ceramic green sheet 22 is formed on the carrier film 14. Next, the rolled-up carrier film is unrolled, and an internal electrode pattern constituting an internal electrode of the laminated ceramic capacitor is printed on the surface of the ceramic green sheet 22 by a printing apparatus 24 The carrier film 14 on which the internal electrode pattern is formed is dried by a drying apparatus 25, and is then taken up in roll form again by the take-up apparatus 26. Furthermore, instead of rolling up the carrier film 14 after the ceramic green sheet has been formed thereon, it is also be possible to continue to print an internal electrode pattern, dry the carrier film, and then roll up the film.
The rolled-up carrier film 14 is subsequently pulled out again, the ceramic green sheet 22 is cut to an appropriate size, and a plurality of the green sheets are laminated. The laminated body formed by laminating the ceramic green sheets 22 is cut into individual elements and fired, so that ceramic sintered bodies having internal electrodes are formed. Laminated ceramic capacitors are manufactured by forming external electrodes on the outer surfaces of the ceramic sintered bodies so that the external electrodes are connected to the internal electrodes.
With the recent trend toward more compact electronic devices, size reduction of laminated ceramic electronic components is required. Laminated ceramic capacitors, for example, are also becoming progressively smaller in size and larger in capacity. Accordingly, the number of layers in a ceramic sintered body is increased, and the thickness of the ceramic layers forming the ceramic sintered body is reduced. In general, however, unevenness inevitably exists on the surfaces of synthetic resin films used as carrier films to form ceramic green sheets. Because of such unevenness, recesses or pinholes may be locally produced in the thinned layers of ceramic green sheets. As a result, problems such as short-circuiting between internal electrodes and a decrease in reliability are encountered in the final product, such as a laminated ceramic capacitor. Thus, the carrier film becomes more susceptible to the effect of surface unevenness by the thinning of ceramic layers.
Therefore, it is necessary to reduce the effect of unevenness by suppressing unevenness on the carrier film surface as much as possible. Incidentally, when a film that is formed into a roll was used as the carrier film to be coated with a ceramic slurry, recesses and pinholes were locally present on the ceramic green sheet even though the surface thereof was made smooth.
As a result of diligent investigations in view of this fact, the present inventors discovered that these problems were caused by the effects of static electricity as described below. In the case of a carrier film roll, the contact area between the overlaid carrier films is increased, so that the carrier film tends to become charged with static electricity when the carrier film is pulled out, thus increasing the electrostatic charge caused by unrolling in this case. Furthermore, because the contact area between the carrier film and the ceramic green sheet is large, the carrier film is apt to be charged with static electricity when the ceramic green sheet is peeled off from the carrier film, which increases the electrostatic charge caused by peeling in this case. The amount of foreign matter mixed inside the ceramic green sheet or laminated body is increased due to the static electricity caused by such charging.
Moreover, a mold release layer or the like that is formed on the ceramic green sheet and carrier film deteriorates due to the discharge of the static electricity caused by charging, so that creases are produced in the ceramic green sheet during peeling. In particular, when the coating rate of the ceramic slurry is increased, because the pulling rate of the carrier film is also increased, the electrostatic charge caused by unrolling is increased, so that the effect of static electricity as described above is increased. As a result, problems such as short-circuiting between internal electrodes and a decrease in reliability occur in the final product such as a laminated ceramic capacitor.
Furthermore, a ceramic slurry is generally applied to the portions of the carrier film excluding both end portions thereof with respect to the direction of width. However, if the unevenness on the surface of the carrier film is reduced, the adhesion characteristics at both end portions are improved when these end portions of the carrier film in the width direction are superimposed during the take-up. Consequently, when the carrier film on which the ceramic green sheet is formed is taken up, air is introduced. If the introduced air escapes during the take-up operation of the carrier film, the roll is misaligned, which creates a problem in that the subsequent handling precision decreases significantly.
Furthermore, when thin ceramic green sheets are formed in order to achieve thinning of ceramic layers, variations in the thickness of the ceramic green sheet can be reduced by increasing the coating rate of the carrier film with the ceramic slurry. Moreover, increasing this coating rate of the ceramic slurry is an essential technique in terms of improving the productivity of laminated ceramic electronic components as well.
In order to overcome the problems described above, preferred embodiments of the present invention provide a method for manufacturing a laminated ceramic electronic component which makes it possible to obtain highly reliable laminated ceramic electronic components even when the coating rate of the surface of the carrier film with the ceramic slurry is increased in order to reduce the thickness of the ceramic green sheet.
According to a preferred embodiment of the present invention, a method for manufacturing a laminated ceramic electronic component includes the steps of pulling out a carrier film from a carrier film roll, coating one surface of the carrier film with a ceramic slurry at a coating rate of about 30 m/min or higher, forming a ceramic green sheet by drying the coated ceramic slurry, forming an internal electrode pattern on the ceramic green sheet, obtaining a laminated body by laminating a plurality of the ceramic green sheets on which the internal electrode patterns are formed, obtaining ceramic sintered bodies by cutting the laminated body into individual elements and firing the individual elements, and forming external electrodes on the outer surfaces of the ceramic sintered bodies, wherein the carrier film has a surface on which the ceramic slurry is coated in which the maximum height Rmax as defined in JIS B0601 is about 0.2 xcexcm or less.
According to another preferred embodiment of the present invention, a method for manufacturing a laminated ceramic electronic component includes the steps of pulling out a carrier film from a carrier film roll, coating one surface of the carrier film with a ceramic slurry at a coating rate of about 30 m/min or higher, forming a ceramic green sheet by drying the coated ceramic slurry, forming an internal electrode pattern on the ceramic green sheet, obtaining a laminated body by laminating a plurality of the ceramic green sheets on which the internal electrode patterns are formed, obtaining ceramic sintered bodies by cutting the laminated body into individual elements and firing the individual elements, and forming external electrodes on the outer surfaces of the ceramic sintered bodies, wherein the carrier film has a surface on which the ceramic slurry is coated in which the maximum height Rmax as defined in JIS B0601 is about 0.2 xcexcm or less, a mold release layer is formed in the ceramic slurry coated surface, and the maximum height Rmax as defined in JIS B0601 of the surface of the carrier film that is opposite to the surface upon which the ceramic slurry is coated is about 0.5 xcexcm to about 1 xcexcm.
According to yet another preferred embodiment of the present invention, a method for manufacturing a laminated ceramic electronic component includes the steps of pulling out a carrier film from a carrier film roll, coating one surface of the carrier film with a ceramic slurry at a coating rate of about 30 m/min or higher, forming a ceramic green sheet by drying the coated ceramic slurry, forming an internal electrode pattern on the ceramic green sheet, obtaining a laminated body by laminating a plurality of the ceramic green sheets on which the internal electrode patterns are formed, obtaining ceramic sintered bodies by cutting the laminated body into individual elements and firing the individual elements, and forming external electrodes on the outer surfaces of the ceramic sintered bodies, wherein the carrier film has a surface on which the ceramic slurry is coated in which a maximum height Rmax as defined in JIS B0601 is about 0.2 xcexcm or less, a mold release layer is formed in the ceramic slurry coated surface, and a maximum height Rmax as defined in JIS B0601 of the surface of the carrier film that is opposite to the surface upon which the ceramic slurry is coated is about 0.2 xcexcm to about 1 xcexcm, and an anti-static layer is formed on at least one surface of the carrier film.
In these methods for manufacturing a laminated ceramic electronic component, it is desirable that the thickness of the ceramic layers defining the ceramic sintered body be about 3 xcexcm or less.
By using the carrier film that has a surface on which the ceramic slurry is coated in which the maximum height Rmax as defined in JIS B0601 is about 0.2 xcexcm or less, recesses and pinholes are prevented from occurring in the ceramic green sheet when the ceramic slurry is applied and dried.
Furthermore, when coating one surface of the carrier film with a ceramic slurry at a coating rate of about 30 m/min or higher, if the maximum height Rmax of the surface of the carrier film that is opposite to surface coated with ceramic slurry is about 1 xcexcm or less, defects in the ceramic green sheet can be prevented during the take-up of the carrier film, and the introduction of air can also be prevented. Moreover, when the maximum height Rmax of the surface of the carrier film that is opposite to the ceramic slurry coated surface is about 0.5 xcexcm or more, the electrostatic charge caused by peeling can be minimized.
In addition, in cases where an anti-static layer is formed on the carrier film, it is possible to further reduce the electrostatic charge caused by peeling if the maximum height Rmax of the surface of the carrier film that is opposite to the ceramic slurry coated surface is about 0.2 xcexcm or more.
These unique advantages and effects are conspicuously apparent when the thickness of the ceramic layers defining the ceramic sintered body of a laminated ceramic electronic component is reduced to about 3 xcexcm or less.
Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.